This invention relates to a doctor blade construction for continuously removing a mud coat from a rotating vacuum drum. The lower portion of the drum is immersed in a bath, the mud containing calcium carbonate which is to be recovered from a mud slurry. The mud is continuously removed from the rotating drum by a doctor blade, with removed mud then passing to a conveyor for further treatment in a lime kiln. In one prior method of recovery, a blade which covered the width of a vacuum drum was advanced toward the drum over a fixed period, typically 10 to 15 minutes. After the blade reached its nearest position to the drum surface, it retracted to its outermost position, with the cycle then repeating. Since the blade was not continuously cutting mud from the vacuum drum surface, the feed to a lime kiln stopped during this time. This introduced a large variation in feed to the lime kiln.
The art is aware of constructions and methods somewhat similar to that of the present invention, such as shown in U.S. Pat. No. 2,857,612 issued to Fisher and U.S. Pat. No. 3,688,337 issued to Noda.